Sheet drying apparatus

ABSTRACT

A sheet drying apparatus having a horizontal drying chamber with a relatively small inlet end and a much larger discharge end. The mechanism which transports successive sheets through the chamber has two transversely extending rolls closely adjacent to the inlet end and two sets of transversely extending rolls adjacent to the discharge end of the drying chamber. The latter is formed with two mirror symmetrical nozzles connected with a source of heated air and having orifices closely adjacent to the path of sheets in the region of the inlet end. The nozzles are formed with projections which cause turbulence in the air streams at the opposite sides of a sheet in the chamber to thus prevent the development of laminar air flow. The cross-sectional area of the discharge end is large enough to allow for practically unobstructed escape of spent air, and the advancing rolls at the discharge end are staggered relative to each other to offer little resistance to the escape of spent air as well as to flex the sheets during travel therebetween. The upper wall of the drying chamber and the corresponding nozzle can be lifted off the lower wall to afford access to the interior of the chamber.

United States Patent Stievenari et al. Feb. 4, 1975 SHEET DRYINGAPPARATUS 3,736,174 5/1973 Moyer 54/155 [75] Inventors: Emile Stievenar,

Miill M h, G Jul-gen umc ermany Attorney, Agent, or Firm-M1chael S.Stnker [73] Ass1gnee: Agfa-Gevaert Alttiengesellschaft, MLlnlCh, GermanyFiledi 1972 A sheet drying apparatus having a horizontal drying 21 A L N300 992 chamber with a relatively small inlet end and a much 1 pp 0 Vlarger discharge end. The mechanism which transports successive sheetsthrough the chamber has two transl l Foreign Application Priority Dataversely extending rolls closely adjacent to the inlet end Oct. 28, 1971Germany 2153752 and two sets of transversely extending rolls adjacent tothe discharge end of the drying chamber. The latter is [52] U.S. Cl34/155, 34/131, 34/156 ormed ith two mirror ymmetrical nozzles con- [5l] Int. Cl. F26b 13/04 nected with a source of heated air and havingorifices [58] Field of Search 34/156, 155; 152, 151, o ely a j cen to hep th of she ts in the region of 34/l48, 160, 162, 154, 153 the inletend. The nozzles are formed with projections which cause turbulence inthe air streams at the oppo- [56] References Cited site sides of a sheetin the chamber to thus prevent the UNITED STATES PATENTS development oflaminar air flow. The cross-sectional 2,577,915 12/1951 Piller =1 al.34/155 area 9 the dscha'ge end large emugh 9 M 2 586 800 2/1952 Elvin e!al 34/155 pract1cally unobstructed escape of spent an, and the 3:293:77512/1966 Kitrosserniz ........II:I 34/156 advancing mus at the dischargeend are staggered 3 3 932 10/1967 Cheape i I 34/155 ative to each otherto offer little resistance to the es- 3,426,441 2/1969 Broski 34/48 pe fspent a r a well as to fle the sheets during 3,545,364 12/1970 Reedy34/155 travel therebetween. The upper wall of the drying 3,548,5l212/l970 Smoot 34/151 hamber and the corresponding nozzle can be lifted3,557,469 Edgmgton off the lower wall to afford access to the interiorof 3,606,689 9/1971 MalSud et 34/155 the chamber 3,707,777 l/l973 Geykenet al 34/l55 I 3,718,983 3/1973 Crowell 34/155 15 Claims, 2 DrawingFigures 1 Ba 15d 15 13 13b 1 snaa'r nnvmc APPARATUS BACKGROUND OF THEINVENTION The present invention relates to apparatus for the drying ofsheet-like materials, such as carriers of exposed and developedphotosensitive layers. More particularly. the invention relates todrying apparatus of the type wherein the sheet-like material to be driedis caused to advance along a predetermined path extending through adrying chamber to be contacted therein by a gaseous drying fluid. Stillmore particularly. the invention relates to improvements in sheet dryingapparatus wherein the material to be dried is transported by two sets ofadvancing rolls located upstream and downstream of the drying chamberand wherein the gaseous drying fluid is admitted by way of nozzleslocated between the front and rear advancing rolls.

In certain presently known sheet drying apparatus, the orifices of thenozzles are located at a considerable distance from the path along whichthe sheet-like material advances through the drying chamber. Also, thedrying chamber is provided with a relatively small single outlet forspent drying fluid. The nozzles are mounted substantially midway betweenthe front and rear advancing rolls. The rate of admission of dryingfluid is such that the pressure in the drying chambers rises aboveatmospheric pressure. It was found that such apparatus cause thegeneration of a relatively slow laminar flow of gaseous fluid along bothsides of a sheet which is being transported through the drying chamber.Such layers of gaseous fluid at both sides of the advancing sheet allowfor a relatively slow drying because they prevent freshly admitted fluidfrom coming into contact with the sheet. Furthermore, automaticthreading of sheets into the drying chamber is not possible because theinterior of the chamber is not provided with sheet guides at any pointbetween the front advancing rolls and the rear advancing rolls.Therefore, the leader of a freshly introduced sheet tends to cling tothe one or the other internal surface of the drying chamber and cannotfind its way into the nip of the rear advancing rolls.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved drying apparatus wherein the leader of a freshlyintroduced sheet to be dried automatically finds its way into the nip ofthe rear advancing rolls without the provision of any guide means in theinterior of the drying chamber and irrespective of the stiffness or lackof stiffness of the sheet material.

Another object of the invention is to provide a drying apparatus whichprevents the development of laminar flow of gaseous drying fluid alongone or both sides of sheets which are caused to advance through thedrying chamber.

A further object of the invention is to provide the drying apparatuswith novel and improved means for insuring continuous contact betweenfresh gaseous drying fluid and sheet material while the materialadvances through the drying chamber.

Still another object of the invention is to provide novel and improvedmeans for admitting a gaseous drying fluid into the chamber of thedrying apparatus.

An additional object of the invention is to provide a drying apparatuswhich can be readily opened to ailow for inspection and cleaning of theinterior of the drying chamber.

The improved drying apparatus comprises a hollow drying chamber having apreferably funnel-shaped inlet end and a discharge end, first rotarysheet advancing means adjacent to the inlet end (and preferablycomprising two rolls at least one of which is driven to rotate the otherroll. either directly or by way of sheet-like material therebetween).second rotary sheet advancing means adjacent to the discharge end anddefining with the first sheet advancing means an elongated path which ispreferably located in a substantially horizontal plane and serves fortravel of sheet-like material into. through and beyond the dryingchamber. a source of gaseous drying fluid. and first and second nozzlemeans provided on the drying chamber adjacent to the inlet end at theopposite sides of the path for sheet-like material and being connectedwith the source of gaseous drying fluid. The nozzle means are preferablymirror symmetrical to each other with reference to the plane of the pathand have orifices closely adjacent to the path and arranged to dischargestreams of gaseous drying fluid against the respective sides ofsheet-like material in the chamber, preferably at least substantially atright angles to the direction of travel of sheet-like material. The thusadmitted streams of drying fluid flow along the sheet-like material inthe chamber and are allowed to escape by way of the discharge end whosecross-sectional area is preferably large enough to allow forsubstantially unobstructed escape of gaseous fluid. The interior of thechamber is provided with means for creating turbulence in the admittedair streams to thus prevent the development of laminar flow of gaseousfluid at one or both sides of the path.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved sheet drying apparatus itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof. will be best understood upon perusualof the following detailed description of certain specific embodimentswith reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary longitudinalvertical sectional view of a drying apparatus which embodies theinvention; and

FIG. 2 is a view as seen in the direction of arrow A in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the sheetdrying apparatus comprises a housing including a lower section 1 and anupper section 3 which is movable relative to the lower section about theaxis of a horizontal pivot member 2. The sections 1 and 3 respectivelysupport the lower and upper portions or walls 12, I3 of a hollowhorizontal drying chamber which walls are respectively provided withgas-admitting nozzles 16 and IS. The lefbhand portion of the lowerhousing section 1, as viewed in FIG. 1, is provided with a vertical slotla which receives the shaft 4 of a lower advancing roll 6 and the shaft5 of an upper advancing roll 7. The preferably horizontal path for thesheets 114 (see FIG. 2) to be dried is indicated by a phantom line 14,and the direction of feed of sheets 114 along the path 14 is indicatedby an arrow B. The path 14 extends through the nip of the advancingrolls 6. 7 and through the interior of the drying chamber.

The lower housing section 1 further supports a horizontal shaft 8 for aset of four discrete axially spaced sheet advancing and flexing rolls9a, 9b. 9c. 9d (see FIG. 2), and the upper housing section 3 supports ashaft for a set of three discrete advancing and flexing rolls lla. llh,llv which alternate with the rolls 9a-9d. as considered at right anglesto the direction of travel of sheets [14 along the path l4. One of theshafts 4,5 and one of the shafts 8J0 is driven by a motor (not shown) oranother suitable prime mover. The directions in which the rolls 6, 7,9u-9d and llal4 llr' rotate when the drying apparatus is in use areindicated by arrows. If the shaft 4 drives the roll 6. the roll 7 isrotated because it rests on the roll 6 or in response to forwardmovement of a sheet 114 along the path 14. Analogously, if the rolls9a-9d are positively driven by the shaft 8. the rolls Ila-11c rotateowing to engagement with the upper side of a sheet 114 in the path 14.

The central portions 122, 13a ofthe walls l2, 13 form a substantiallyhorizontal nozzle whose cross-sectional area decreases in a directionfrom the advancing rolls 6, 7 toward the advancing rolls 9a-9d, 110-110,i.e., in the direction (arrow B) of lengthwise movement of sheets 114.The front or foremost portions 12a, 13a of the walls 12, 13 constitute afunnel-shaped inlet end of the drying chamber which is locatedimmediately downstream of or close to the advancing rolls 6, 7 and whosecross-sectional area decreases in the same direction as thecross-sectional area of the nozzle defined by the median portions 12e,13a of the walls 12, 13. The arcuate rightmost or rearmost portions 12b,13b of the walls 12, 13 form a discharge end which surrounds, withconsiderable clearance, portions of the advancing rolls 9a-9d andlla-llc.

The nozzle admits a gaseous drying fluid (e.g.. air) in the directionindicated by arrow C. The arrow D indicates the direction of admissionof drying fluid by way ofthe nozzle 16. As shown in FIG. 1, thedirection of gas flow toward the path i4 is substantially or exactly atright angles to the direction oflengthwise travel of sheets 114 (arrowB). The portions 15a. 16a of the nozzles l5. 16 preferably extend veryclose to the path 14 and are located at the upstream sides of therespective gas-discharging orifices 15d and 1641. The portions orprojections 15b. 16b of the nozzles l5, 16 are more distant from thepath 14 and constitute preferably rounded protuberances which createturbulence in the streams of gaseous drying fluid respectively flowingalong the upper and lower sides of sheets 114 in the path 14. lt will benoted that each ofthe nozzle portions lSb. 16b extends somewhat beyondthe adjacent central portion 13a, 12a of the respective wall l3, 12. Thejust described configuration of those portions of the nozzles 15, 16which respectively define the orifices l5d. 16d brings about a desirableturbulence and also effects a pronounced deflection of inflowing gaseousfluid through approximately 90 i.e., the two streams of gaseous fluidfirst flow at right angles to and thereupon in substantial parallelismwith the path 14. The helical arrows shown in FIG. 1 indicate the areaswhere the turbulent gaseous fluid develops a dynamic pressure orvelocity head and flows through the horizontal nozzle l2e. l3e of thedrying chamber toward the discharge end defined by the arcuate portions12b, 13b. It was found that the drying action of a gaseous fluid isespecially satisfactory if the speed of fluid streams in the centralportion of the drying chamber formed by the walls l2, I3 is between 8and 15 meters per second.

The central portion of the lower wall 12 is further provided with arecess 12d for a temperature measuring gauge 12c (e.g., an NTC-resistor)which controls the temperature of the gaseous fluid supplied to thenozzles 15 and 16 by a blower 50 or an analogous source. The gauge 12-can furnish signals to a transducer 5| which controls a heating device(not shown) for gaseous fluid flowing into or issuing from the blower50.

An important advantage of the improved drying apparatus is that the twomirror symmetrical nozzles l5. l6 are immediately or closely adjacent tothe funnelshaped inlet end 12a. 13a of the drying chamber and that theorifices 15d. 16d are closely or immediately adjacnt to the respectivesides of the path 14. The crosssectional area of the narrowest part ofthe inlet end 120. 13a is much smaller than the cross-sectional area ofthe narrowest part of the discharge end 12h, 13b of the drying chamberand the narrowest portion of the cross-sectional area of the dischargeend 12h. 13b is sufficient to allow for practically unobstructed escapeof spent gaseous fluid from the chamber.

The turbulence which is caused by the projections 15b, 16b of thenozzles 15, 16(these projections can be said to form part of the dryingchamber since the nozzles 15, 16 are shown as being integral with therespective walls l3, l2) insures that the fluid which is admit ted intothe chamber cannot form a laminar flow at the respective sides of sheets114 which are being transported along the path 14 so that each portionof a sheet in the drying chamber is continuously contacted by freshgaseous fluid to thus insure a highly satisfactory removal of moisture.This, in turn. renders it possible to reduce the overall length of thedrying apparatus (as considered in the direction of arrow B) because thewithdrawal of desired quantities of moisture from sheets in the chambercan be completed within surprisingly short intervals of time. Theaforementioned dynamic pressure which develops in the regions where thestreams issuing from the orifices 15d. 16d impinge on the respectivesides of a sheet H4 in the drying chamber drops rapidly in a directiontoward the relatively large discharge end 15b. 16b of the dryingchamber. It was further found that, if a sheet 114 in the drying chambertends to leave the path 14 by flexing toward the wall 12 or 13, thedynamic pressure at the side of the path where the sheets deviates fromits prescribed route remains intact much longer than at the other sideof the path and automatically compels the sheet to return into the path14. Thus. if the leading end of a freshly introduced sheet 114 tends toflex sideways after it has moved through the inlet end 12a, 13a andbeyond the space between the nozzles 15d, 16d. the leading end issubjected to the action of a relatively strong force which tends to moveit into the path [4. This is highly desirable because the streams ofgaseous drying fluid which are admitted into the chamber by way of theorifices 15d, 16d bring about an automatic threading action to thusinsure that the leader of a freshly inserted sheet 114 automaticallyfinds its way into the space between the rolls 9u-9d and Ila-11c. Suchautomatic threading takes place without necessitating the provision ofany mechanical or other guide means in the interior of the dryingchamber.

The feature that the median portions 12a, 134 of the walls l2, l3converge toward each other in the direction indicated by the arrow Bcontributes to acceleration of gas streams during flow toward thedischarge end 12!), 13b.

The rollers 6, 7 are preferably placed so close to the inlet end 120,13a that they invariably prevent the escape of substantial quantities ofgaseous drying fluid counter to the direction of transport of sheets II4 through the drying chamber. 0n the other hand, the transverselystaggered rollers 9a-9d and llal lc' provide a number of passagesthrough which the spent gaseous fluid can escape by way of the dischargeend 12b. 13b. It will be seen that the distance between the common axisof the rolls 9a-9d and the common axis of the rolls Ila-11c is less thanthe diameter of a roll 9 or II. Consequently, a sheet 114 which iscaused to pass between the rolls 9a-9d and Ila-l lc is flexed to assumea meandering shape and to increase the friction between its material andthe peripheral surfaces of the rolls 9a-9d and Ila-11c. This insuresorderly withdrawal of sheets 114 from the drying chamber.

The minimum cross-sectional area of the funnelshaped inlet end 120, 13ais preferably selected in such a way that the leader of a sheet 114which has been introduced through the inlet end automatically finds itsway into the space between the orifices 15d, 16d whereby the streamsof'gaseousdrying fluid insure that the leader of the sheet 114 remainsin the path 14 and advances toward the space between the rolls 9a-9d andIla-11c. This allows for a fully automatic threading operation,especially if the apparatus is further provided with a feeder (notshown) which feeds sucessive sheets H4 into the nip of the advancingrolls 6, 7. If a sheet 114 happens to jam in the interior of the dryingchamber, the operator merely lifts the wall 13 and the nozzle 15 abovethe wall 12 by pivoting the housing section 3 about the axis of thepivot member 2. The wall 13 then affords convenient access to theinterior of the drying chamber. Such access to the interior of thedrying chamber is desirable on the additional ground that a person incharge can inspect the internal surfaces of the walls l2. 13 to detecteventual deposition of chemicals which are carried by the sheets 114.

Without further analysis. the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly consitute essential characteristics of the generic andspecific aspects of our contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

I. Apparatus for drying sheet-like materials, comprising a hollow dryingchamber having an inlet end and a discharge end. the cross-sectionalarea of said inlet end being substantially smaller than thecross-sectional area of said discharge end; first rotary sheet advancingmeans comprising a pair of rolls closely adjacent to said inlet end;second rotary sheet advancing means adjacent to said discharge end anddefining with said first sheet advancing means an elongated path fortravel of sheet-like material into, through and beyond said chamber; asource of gaseous drying fluid; and first and second nozzle meansprovided on said chamber adjacent to said inlet end at the oppositesides of said path and connected with said source. said nozzle meanshaving orifices closely adjacent to said path and arranged to dischargestreams of gaseous drying fluid against the respective sides ofsheet-like material in said chamber whereby the drying fluid flows alongthe sheetlike material to leave said chamber by way of said dischargeend. the cross-sectional area of said discharge end being large enoughto allow for substantially unobstructed escape of gaseous fluid which isadmitted into said chamber by said nozzle means and the crosssectionalarea of said chamber decreasing in a direction from said orifices towardsaid discharge end to a point near the discharge end and then increasingin crosssectional area to the discharge end. said second sheet advancingmeans comprising first and second roll means located at opposite sidesof said path. said first and second roll means defining a plurality oflarge passages so as to offer little resistance to escape of gaseousdrying fluid by way of said discharge end.

2. Apparatus as defined in claim I, wherein said nozzle means arearranged to admit said streams of gaseous drying fluid at a speed of8-l5 meters per second.

3. Apparatus as defined in claim I, wherein said chamber is providedwith internal projections located downstream of said orifices, asconsidered in the direction of travel of sheet-like material, to produceturbulence in said streams.

4. Apparatus as defined in claim 3, wherein said nozzle means areintegral with said chamber and said projections are provided on saidnozzle means in the region of the respective orifices.

5. Apparatus as defined in claim I, further comprising control means forregulating the temperature of gaseous drying fluid which is furnished bysaid source. said control means comprising temperature measuring meansprovided in said chamber.

6. Apparatus as defined in claim 5. wherein said chamber comprises anupper portion located above and a lower portion located below said path.said temperature measuring means comprising an NTC-resistor installed insaid lower portion of said chamber.

7. Apparatus as defined in claim I, wherein said first sheet advancingmeans comprises a pair of elongated rolls located at the opposite sidesof and extending across the full width of said path.

'8. Apparatus as defined in claim 7, wherein said rolls are closelyadjacent to said inlet end so as to prevent escape of substantialquantities of gaseous drying fluid from said chamber by way of saidinlet end.

9. Apparatus as defined in claim I wherein said first roll means of saidsecond sheet advancing means comprises at least two axially spaced firstrolls located at one side of said path and said second roll means ofsaid second sheet advancing means comprises at least one second rolllocated at the opposite side of said path, said first and second rollsbeing staggered relative to each other, as considered at right angles tothe direction of travel of sheet-like material along said path.

10. Apparatus as defined in claim 9, wherein the distance between theaxes of said first and second rolls is less than the diameter of one ofsaid rolls so that said rolls effect at least some flexing of sheet-likematerial during travel of such material between said first and secondrolls.

a first section connected to said first wall and a second sectionconnected to and movable with said second wall.

l4. Apparatus as defined in claim [2, wherein said first and secondnozzle means are repsectively provided on said first and second walls.

15. Apparatus as defined in claim I, wherein said first nozzle means ismirror symmetrical to said second nozzle means with reference to theplane of said path.

1 i i i

1. Apparatus for drying sheet-like materials, comprising a hollow dryingchamber having an inlet end and a discharge end, the cross-sectionalarea of said inlet end being substantially smaller than thecross-sectional area of said discharge end; first rotary sheet advancingmeans comprising a pair of rolls closely adjacent to said inlet end;second rotary sheet advancing means adjacent to said discharge end anddefining with said first sheet advancing means an elongated path fortravel of sheet-like material into, through and beyond said chambeR; asource of gaseous drying fluid; and first and second nozzle meansprovided on said chamber adjacent to said inlet end at the oppositesides of said path and connected with said source, said nozzle meanshaving orifices closely adjacent to said path and arranged to dischargestreams of gaseous drying fluid against the respective sides ofsheet-like material in said chamber whereby the drying fluid flows alongthe sheetlike material to leave said chamber by way of said dischargeend, the cross-sectional area of said discharge end being large enoughto allow for substantially unobstructed escape of gaseous fluid which isadmitted into said chamber by said nozzle means and the cross-sectionalarea of said chamber decreasing in a direction from said orifices towardsaid discharge end to a point near the discharge end and then increasingin cross-sectional area to the discharge end, said second sheetadvancing means comprising first and second roll means located atopposite sides of said path, said first and second roll means defining aplurality of large passages so as to offer little resistance to escapeof gaseous drying fluid by way of said discharge end.
 2. Apparatus asdefined in claim 1, wherein said nozzle means are arranged to admit saidstreams of gaseous drying fluid at a speed of 8-15 meters per second. 3.Apparatus as defined in claim 1, wherein said chamber is provided withinternal projections located downstream of said orifices, as consideredin the direction of travel of sheet-like material, to produce turbulencein said streams.
 4. Apparatus as defined in claim 3, wherein said nozzlemeans are integral with said chamber and said projections are providedon said nozzle means in the region of the respective orifices. 5.Apparatus as defined in claim 1, further comprising control means forregulating the temperature of gaseous drying fluid which is furnished bysaid source, said control means comprising temperature measuring meansprovided in said chamber.
 6. Apparatus as defined in claim 5, whereinsaid chamber comprises an upper portion located above and a lowerportion located below said path, said temperature measuring meanscomprising an NTC-resistor installed in said lower portion of saidchamber.
 7. Apparatus as defined in claim 1, wherein said first sheetadvancing means comprises a pair of elongated rolls located at theopposite sides of and extending across the full width of said path. 8.Apparatus as defined in claim 7, wherein said rolls are closely adjacentto said inlet end so as to prevent escape of substantial quantities ofgaseous drying fluid from said chamber by way of said inlet end. 9.Apparatus as defined in claim 1 , wherein said first roll means of saidsecond sheet advancing means comprises at least two axially spaced firstrolls located at one side of said path and said second roll means ofsaid second sheet advancing means comprises at least one second rolllocated at the opposite side of said path, said first and second rollsbeing staggered relative to each other, as considered at right angles tothe direction of travel of sheet-like material along said path. 10.Apparatus as defined in claim 9, wherein the distance between the axesof said first and second rolls is less than the diameter of one of saidrolls so that said rolls effect at least some flexing of sheet-likematerial during travel of such material between said first and secondrolls.
 11. Apparatus as defined in claim 1, wherein said inlet endconstitutes a funnel whose cross-sectional area decreases in thedirection of transport of sheet-like material therethrough. 12.Apparatus as defined in claim 1, wherein said chamber comprises aplurality of walls including a first wall and a second wall movablerelative to said first wall to afford access to the interior of saidchamber.
 13. Apparatus as defined in claim 12, further comprising ahousing supporting said chamber and having a first sectiOn connected tosaid first wall and a second section connected to and movable with saidsecond wall.
 14. Apparatus as defined in claim 12, wherein said firstand second nozzle means are repsectively provided on said first andsecond walls.
 15. Apparatus as defined in claim 1, wherein said firstnozzle means is mirror symmetrical to said second nozzle means withreference to the plane of said path.